I’m still seeing PDF documents in the zip folder that downloaded to my device and in many cases, no EPUB file?

There are several possibilities here:

• The study that you downloaded may have been processed prior to July 2024. ICPSR is not converting old PDF codebooks to EPUB files. Only new studies processed and released from July 2024 forward will receive the EPUB codebook file.
• Sometimes data producers provide research materials in PDF that they desire to be shared (e.g., questionnaire, project notes, etc.). These documents are included in the folder in PDF format.
• For ease of printing, most projects are providing a PDF codebook in addition to the EPUB codebook in the download folder.